expect(subject, assertionName, [value, ...])
Perform an assertion about
expect function will throw an
UnexpectedError if the assertion can be
decided synchronously and isn't fulfilled:
In all other cases
expect will return a
Bluebird promise which will either be
rejected or fulfilled. For consistency, even successful synchronous assertions will
return a promise.
The idea is that you can return the promise to your test framework (from an
block or equivalent), so that the outcome of the test will be decided by whether
the promise is fulfilled. This works natively in mocha 1.18+, and Unexpected
does some unholy trickery so it also works in Jasmine.
Note that if the assertion is asynchronous, you'll have to return the promise
Otherwise your test framework will assume that the test has passed and won't wait for the asynchronous work to complete.
As of 8.0.0 Unexpected will detect created promises that were never returned and make the test fail synchronously. This will uncover some extremely nasty bugs where the test suite succeeds when it should actually fail. However, this feature only works in Mocha and Jasmine.
expect(...).and(assertionName, [value, ...])
The returned promise will be augmented with an
and method that allows you to
perform more assertions on the same subject:
Again, note that you need to return the value returned by
expect to your
block if any of the assertions are asynchronous: